Fuel rail vapor bleed

ABSTRACT

In an internal combustion engine fuel injection system, a vacuum operated valve opens during closed throttle engine operation to permit fuel vapor to bleed from the end of the pressurized fuel rail back to the fuel tank.

Unite States Patent [191 Moulds Feb. 5, 1974 FUEL RAIL VAPOR BLEED John W. Moulds, Penfield, NYv

General Motors Corporation, Detroit, Mich.

Filed: Jan. 28, 1972 Appl. No.: 221,640

Inventor:

Assignee:

US. Cl. 123/140 MP, 123/119 R, 123/139 AW,

Int. Cl. F02m 5/06 Field of Search. 123/139 AW, 119 R, 140 MC, 123/32 EA References Cited UNITED STATES PATENTS Dermond 123/139 AW 3,596,640 8/1971 Bloomfield 123/1 19 R 3,500,803 3/1970 Long 123/32 EA 2,902,016 9/1959 Powell et al 123/139 AW 3,608,531 9/1971 Baxendale 123/139 AW Primary Examiner-Laurence M. Goodridge Attorney, Agent, or Firm-C. K. Veenstra [57] ABSTRACT 4 Claims, 6 Drawing Figures 2U 10 l I U PATENTEI] FEB 51974 sum 2 or 4 FUEL RAIL VAPOR BLEED This invention relates to means for bleeding fuel vapor from an internal combustion engine fuel supply system and, more particularly, to means for opening the vapor bleed only during closed throttle engine operation.

In the operation of carburetted internal combustion engines, it has been common practice to utilize a fuel vapor return line which bleeds fuel vapor from a point in the fuel line between the fuel pump and the carburetor fuel bowl and recirculates the fuel vapor back to the fuel tank. Such is effective in preventing an accumulation of fuel vapor which could cause vapor lock in that portion of the fuel line. While in conventional usage the vapor return line is continuously open for recirculation of fuel vapor back to the fuel tank, at least one prior art reference has proposed that the vapor return line be closed under all but high temperature conditions.

In the development of a fuel injection system, certain conditions of pressure and. temperature were encountered under which it seemed advisable to provide a similar vapor bleed for removing fuel vapors from the fuel rail which supplies fuel from the injection pump to the fuel injection nozzles. In general, however, and particularly in connection with fuel injection systems which operate at elevated pressures, it is considered undesirable to provide a vapor return line because the vapor return line requires the pump to deliver additional fuel and because as fuel passes from the fuel rail into the vapor return line additional vapor is generated due to the decrease in pressure.

This invention makes possible the resolution of these conflicting considerations by preventing an undesired accumulation of fuel vapor in the fuel rail while at the same time minimizing recirculation of liquid fuel. This invention provides a valve which controls the vapor bleed opening from the fuel rail into the recirculation line, permitting recirculation of fuel vapor only when the engine is operating under closed throttle conditions.

The details as well as other objects and advantages of this invention are set forth in the remainder of the specification and are set forth in the drawings in which:

FIG. I is a schematic view of a fuel injection system incorporating this invention;

FIG. 2 is a top plan view of a fuel injection system showing the fuel rail and the vapor bleed control unit mounted thereon;

FIG. 3 is a sectional view along line 3-3 of FIG. 2 showing the construction of the vapor bleed control unit;

FIG. 4 is a sectional view along line 4-4 of FIG. 3 showing additional details of the construction of the unit;

FIG. 5 is a sectional view along line 5-5 of FIG. 2 showing the manner of mounting the fuel injector in the fuel rail; and

FIG. 6 is a sectional view along line 6-6 of FIG. 5 showing the construction of the fuel injector.

Referring first to FIGS. 1 and 2, a fuel injection pump 10 receives fuel through a fuel line 12 from a fuel tank 14. Injection pump it) delivers fuel through a line 16 to a fuel rail 18 and, through a crossover line 20, to a second fuel rail 22. A plurality of fuel injectors 24 deliver fuel from fuel rails 18 and 22 to the engine induction passage 26 adjacent the inlet valve 28 for each combustion chamber.

A crossover line 30 joins the opposite ends of fuel rails 18 and 22, and a fuel rail vapor bleed control unit 32 is mounted at the end of fuel rail 22. When open, bleed control unit 32 permits fuel vapor to be dis charged from the ends of fuel rails 18 and 22 through a vapor return line 34 back to fuel tank 14. It will be appreciated that, under some circumstances, fuel return line 34 could discharge into the inlet of pump 10 or directly into inlet manifold 26, rather than back to fuel tank 14.

As schematically shown in FIG. I, bleed control unit 32 comprises a valve 36 which opens an orifice 38 to permit discharge of fuel into the vapor return line 34. Valve 36 is opened by a diaphragm 40 against the bias of a spring 42. Diaphragm 40 is actuated against the bias of spring 42 by a manifold vacuum signal received through a line 44 extending from intake manifold 26 below the throttle 46. A second vacuum line 48 extends tothe opposite side of diaphragm 40 from a port 50 disposed in manifold 26 adjacent the upstream edge 52 of throttle 46. When throttle 46 is open, its upstream edge 52 traverses port 50 and the pressure in the chamber 54 on one side of diaphragm 40 is equalized with the pressure in the chamber 56 on the other side of diaphragm 40. Under these conditions, spring 42 closes valve 36 to prevent recirculation of fuel vapor. When the engine is operating and throttle 46 is closed to the position shown, chamber 54 is subjected to the essentially atmospheric pressure upstream of throttle 46 and chamber 56 is subjected to the manifold vacuum down stream of throttle 46; the difference thcrebetween then draws diaphragm 40 against the bias of spring 42 and valve 36 is opened.

It will be appreciated that bleed control unit 32 is effective to prevent recirculation of fuel vapor and thus to prevent dissipation of pressure in fuel rails I8 and 22 whenever the engine is not operating, as well as during open throttle engine operation.

Referring now to FIG. 2, a throttle body unit 58 contains throttles 46 which control the admission of air to induction passages 26. Throttle body 58 also includes means, not here important, for measuring the rate of air flow into induction passages 26.

Fuel rails 18 and 22 are disposed along opposite sides of the engine. The right-hand end of fuel rail 18 includes a housing 60 for a fuel filter which receives fuel from injection pump It) through fuel line 16 and which discharges fuel into fuel rail 18 and through crossover line 20 into fuel rail 22. The right-hand end of fuel rail 22 has a fitting 62 for receiving fuel from crossover line 20. At the left-hand end of fuel rail 18 is a fitting 64 for discharging fuel into crossover line 30. Fitting 64 may include provision for mounting a thermistor 66 to measure fuel temperature.

Bleed control unit 32 is mounted as a fitting on the left-hand end of fuel rail 22 to receive fuel both from fuel rail 22 and from crossover line 30. As shown in FIGS. 3 and 4, bleed control unit 32 includes a body 68 having an inlet 70 from crossover line 30 and an inlet 72 from fuel rail 22. Inlets 70 and 72 lead to a passage 74 in which orifice 38 is located. An annular valve seat 76 is disposed at the upper end of passage 74 and is controlled by valve member 36 which preferably is flat as shown here. Valve member 36 is mounted on the end of a piston 78 which is secured to diaphragm 40.

An outlet 80 (FIG. 4) leads from the annular space 82 surrounding valve seat 76 to fuel return line 34.

As shown in FIG. 3, a spring biased ball check valve 84 is opened by excess fuel pressure in passage 74 to permit fuel to be discharged from passage 74 through an opening 86, the check valve chamber 88, and an opening 90 into annular chamber 82. Thus excess pressure is relieved through outlet 80 and fuel return line 34.

As may be seen from FIG. 2, a plurality of injection nozzles 24 are disposed in each fuel rail 18 and 22. FIG. shows the manner in which injectors 24 are received by the fuel rails. Each fuel rail is an aluminum extrusion having a fuel passage 92 and an air passage 94. Fuel passages 92 receive fuel from injection pump at one end and deliver fuel past the injection nozzles 24 to the other end. Air passages 94 receive air through fittings 96 shown in FIG. 2.

Injector sockets 98 are formed in the fuel rails to intersect fuel passages 92. A critical flow nozzle 100 opens from the base of each injector socket 98, and drilled passages 102 communicate the base of each in jector socket 98 with air passages 94. Injection nozzles 24 control the delivery of fuel from fuel passages 92 and direct the fuel through critical flow nozzles 100 into induction passages 26.

As shown in FIG. 6, the housing 104 of injection nozzle 24 has an inlet 106 which receives fuel from injector socket 98 through a filter 108. When the injection valve 110 is lifted, fuel is discharged from inlet 106 through an outlet 112 to orifice 100. At its upper end, valve 110 has an electromagnetically responsive armature 114 which is lifted when a coil 116 is energized.

From the foregoing, it will be appreciated that this invention provides a fuel injection system in which an injection pump circulates fuel through a pair of fuel rails past a plurality of injectors located in each. During engine idling operation, which when prolonged is most likely to create an accumulation of fuel vapor in the fuel rails, a bleed control unit opens to permit any such fuel vapor to be discharged from the fuel rails and recirculated to the fuel tank.

I claim:

1. In an internal combustion engine having an induction passage for air flow to the engine and a throttle disposed in said induction passage and controlling air flow therethrough: a fuel injection system comprising a plurality of injection nozzles, a fuel rail connected to said nozzles at spaced locations along said rail for delivering fuel to said nozzles, a fuel pump connected to one end of said rail for delivering fuel therethrough, an atmospheric pressure air passage disposed between said nozzles and said induction passage, said nozzles discharging fuel through said air passage into said induction passage, means defining a bleed opening at the other end of said rail for permitting fuel vapor to escape from said rail, and means associated with said bleed opening for permitting flow therethrough only when the engine is running and said throttle is closed.

2. The method of operating an internal combustion engine having an induction passage for air flow to the engine, a throttle disposed in said induction passage and movable between opened and closed positions for controlling air flow therethrough, a fuel rail, a plurality of fuel injection nozzles connected to said fuel rail at spaced locations therealong for delivering fuel to the engine, an atmospheric pressure air passage disposed between said nozzles and said induction passage, said nozzles discharging fuel through said air passage into said induction passage, and a fuel pump for delivering fuel to one end of said fuel rail from a source of fuel, said method comprising the steps of recirculating fuel vapor from the other end of said fuel rail to said source only when said engine is running and said throttle is closed, and preventing recirculation of fuel vapor from said other end of said fuel rail to said source at all other times.

3. In an internal combustion engine having an induction passage for air flow to the engine, a throttle disposed in said induction passage and movable between open and closed positions for controlling air flow therethrough, a fuel rail for fuel flow to the engine and having an inlet, and a fuel pump for delivering fuel to said inlet: a fuel rail vapor bleed comprising means defining a bleed opening for permitting fuel vapor to escape from said fuel rail, a valve associated with said opening for controlling the flow of fuel vapor therethrough, and valve operating means associated with said valve and with said throttle, said valve operating means comprising a spring biasing said valve toward a closed position in which said valve prevents escape of fuel vapor through said opening, a pressure responsive diaphragm operative to move said valve against the bias of said spring to an open position in which said valve permits escape of fuel vapor through said opening, means subjecting one side of said diaphragm to the pressure in said induction passage downstream of said throttle whereby said diaphragm is drawn in a valve opening direction, and means subjecting the other side of said diaphragm to the pressure in said induction passage up stream of said throttle when said throttle is closed and downstream of said throttle when said throttle is open, whereby said diaphragm moves said valve to an open position only when said engine is running and said throttle is closed and whereby the pressure on each side of said diaphragm is balanced both when said engine is running and said throttle is open and when said engine is not running to thereby permit said spring to move said valve to a closed position.

4. In an internal combustion engine having an induction passage for air flow to the engine and a throttle disposed in said induction passage and controlling air flow therethrough: a fuel injection system comprising a pair of fuel rails, a first group of fuel injection nozzles connected to one of said rails at spaced locations therealong to receive fuel therefrom, a second group of fuel injection nozzles connected to the other of said rails at spaced locations therealong to receive fuel therefrom, first and second atmospheric pressure air passages disposed respectively between said induction passage and said first and second groups of nozzles, said nozzles discharging fuel through said air passages into said induction passage, a fuel pump connected to one end of said rails for delivering fuel therethrough, means defining a bleed opening connected to the opposite end of said rails for permitting fuel vapor to escape from said rails, and means associated with said bleed opening for permitting flow therethrough only when said engine is running and said throttle is closed. 

1. In an internal combustion engine having an induction passage for air flow to the engine and a throttle disposed in said induction passage and controlling air flow therethrough: a fuel injection system comprising a plurality of injection nozzles, a fuel rail connected to said nozzles at spaced locations along said rail for delivering fuel to said nozzles, a fuel pump connected to one end of said rail for delivering fuel therethrough, an atmospheric pressure air passage disposed between said nozzles and said induction passage, said nozzles discharging fuel through said air passage into said induction passage, means defining a bleed opening at the other end of said rail for permitting fuel vapor to escape from said rail, and means associated with said bleed opening for permitting flow therethrough only when the engine is running and said throttle is closed.
 2. The method of operating an internal combustion engine having an induction passage for air flow to the engine, a throttle disposed in said induction passage and movable between opened and closed positions for controlling air flow therethrough, a fuel rail, a plurality of fuel injection nozzles connected to said fuel rail at spaced locations therealong for delivering fuel to the engine, an atmospheric pressure air passage disposed between said nozzles and said induction passage, said nozzles discharging fuel through said air passage into said induction passage, and a fuel pump for delivering fuel to one end of said fuel rail from a source of fuel, said method comprising the steps of recirculating fuel vapor from the other end of said fuel rail to said source only when said engine is running and said throttle is closed, and preventing recirculation of fuel vapor from said other end of said fuel rail to said source at all other times.
 3. In an internal combustion engine having an induction passage for air flow to the engine, a throttle disposed in said induction passage and movable between open and closed positions for controlling air flow therethrough, a fuel rail for fuel flow to the engine and having an inlet, and a fuel pump for delivering fuel to said inlet: a fuel rail vapor bleed comprising means defining a bleed opening for permitting fuel vapor to escape from said fuel rail, a valve associated with Said opening for controlling the flow of fuel vapor therethrough, and valve operating means associated with said valve and with said throttle, said valve operating means comprising a spring biasing said valve toward a closed position in which said valve prevents escape of fuel vapor through said opening, a pressure responsive diaphragm operative to move said valve against the bias of said spring to an open position in which said valve permits escape of fuel vapor through said opening, means subjecting one side of said diaphragm to the pressure in said induction passage downstream of said throttle whereby said diaphragm is drawn in a valve opening direction, and means subjecting the other side of said diaphragm to the pressure in said induction passage upstream of said throttle when said throttle is closed and downstream of said throttle when said throttle is open, whereby said diaphragm moves said valve to an open position only when said engine is running and said throttle is closed and whereby the pressure on each side of said diaphragm is balanced both when said engine is running and said throttle is open and when said engine is not running to thereby permit said spring to move said valve to a closed position.
 4. In an internal combustion engine having an induction passage for air flow to the engine and a throttle disposed in said induction passage and controlling air flow therethrough: a fuel injection system comprising a pair of fuel rails, a first group of fuel injection nozzles connected to one of said rails at spaced locations therealong to receive fuel therefrom, a second group of fuel injection nozzles connected to the other of said rails at spaced locations therealong to receive fuel therefrom, first and second atmospheric pressure air passages disposed respectively between said induction passage and said first and second groups of nozzles, said nozzles discharging fuel through said air passages into said induction passage, a fuel pump connected to one end of said rails for delivering fuel therethrough, means defining a bleed opening connected to the opposite end of said rails for permitting fuel vapor to escape from said rails, and means associated with said bleed opening for permitting flow therethrough only when said engine is running and said throttle is closed. 